After three successful years, Mercedes-Benz has overhauled the design and engineering of the B-Class. The facelift programme focused on environmental compatibility, economic efficiency and comfort, with further advances being made in each of these areas. Thanks to a series of detailed improvements, the four-cylinder engines now burn up to seven percent less fuel than previously, and distinguish themselves with remarkably low exhaust emissions that undercut the current EU limits by as much as 90 percent. Mercedes-Benz has developed a new ECO start/stop function for the high-volume B 150 and B 170 models. This switches off the engine when stopped at traffic lights, for example, producing a fuel saving of up to nine percent in practical use. Additional new developments include active parking assist which helps drivers to both find a suitable parking spot, and then manoeuvre into it.

The sales figures for the B-Class to date provide clear evidence that the Mercedes-Benz product planners hit the mark with a concept that caters to the motoring needs of today's sophisticated society: since mid-2005, over 325,000 motorists around the world have been won over by the Sports Tourer.

Diesel engines: fuel consumption reduced by a further seven percent

The B-Class continues to be available with a choice of six engines – two direct-injection diesel units (109 hp and 140 hp) delivering up to 300 Nm of torque, as well as four petrol engines with a peak power output of up to 193 hp and a maximum torque of 280 Nm. The four-cylinder power units have undergone a series of detailed improvements in order to further reduce fuel consumption.

For the diesel models, this means that the combined NEDC fuel consumption
of the B 180 CDI and B 200 CDI has dropped by as much as seven percent – depending on tyre size – to 52.3 - 54.3 mpg and 50.4 - 52.3 mpg, respectively. The two turbodiesel models will therefore be an even less seldom sight at the filling station from now on; the B 180 CDI can clock up over 620 miles on a single tank of fuel (54 litres).

Petrol models: new fuel-saving ECO start/stop function

Depending on the model and engine output, the four petrol variants of the B-Class return fuel consumption figures of between 34.9 - 42.8 mpg on the NEDC driving cycle. From autumn 2008, motoring is set to become even more economical with the arrival of the B 150 and B 170 BlueEFFICIENCY models featuring the ECO start/stop function (optional). This newly developed function automatically switches the engine off when the driver shifts to neutral at low speed whilst depressing the brake pedal. If the criteria for stopping the engine are fulfilled, a special display appears in the instrument cluster to inform the driver.

The moment the clutch is pressed or the brake pedal released, the engine springs back to life almost noiselessly and in a fraction of a second. This ability to restart the engine swiftly yet smoothly gives the ECO start/stop function a key edge over other systems of this type. To achieve this, Mercedes-Benz fits a starter-generator which is connected to the crankshaft via the belt drive. This allows the engine to start much faster and far more quietly than with the conventional starter. During the journey, the starter-generator feeds the electrical system on board the B-Class with energy.

In practical operation, substantial fuel savings of up to nine percent can be achieved with the ECO start/stop function, particularly when driving in city traffic with frequent stops at traffic lights or in tailbacks.

Key B-Class engine, performance and fuel consumption figures at a glance: